The International Journal of Oral & Maxillofacial Implants, 02/2003

Purpose: The aim of the present study was to evaluate longitudinally the stability of a cohort of esthetic implants that had been in function for at least 1 year prior to the baseline examination. Materials and Methods: Sixty-one maxillary anterior ITI implants in 45 systemically healthy patients, supporting single crown restorations, were randomly selected and examined. Clinical, microbiologic, and biochemical parameters were recorded at baseline and again after 3 years. Clinical examination included Plaque Index, Gingival Index, bleeding on probing, probing pocket depth (PPD), distance between implant shoulder and mucosal margin (DIM), and mobility. Dark-field microscopy and immunofluorescence were used to evaluate the bacteria morphotypes and the presence of 5 specific pathogenic bacteria, respectively. Peri-implant crevicular fluid (PICF) was collected at the mesial and distal sites of each implant, and total amounts of 3 biochemical markers were assessed: alkaline phosphatase was measured by using p-nitrophenyl-phosphate as substrate, elastase activity was measured by the use of a low-molecular-weight fluorogenic substrate, and the inhibitor α2-macroglobulin (α2M) was measured by enzyme-linked immunosorbent assay. Results: The only statistically significant differences between baseline and follow-up examination concerned PPD and DIM measurements, which increased slightly. The remainder of the clinical measurements and almost all of the microbiologic and biochemical parameters did not change significantly. Furthermore, no associations were observed between the above results and the number of years that implants had been in function. Discussion and Conclusions: Based on an observation period of 4 to 9 years (mean 6.8 years at the time of the follow-up examination), it can be concluded that in patients with appropriate oral hygiene, the intracrevicular position of the restoration margin does not appear to adversely affect peri-implant health and stability.

Purpose: Bioresorbable bone graft substitutes could eliminate disadvantages associated with the use of autografts, allografts, and other synthetic materials. The authors investigated the osteoinductive capacity of a bioresorbable bone graft substitute made from the unsaturated polyester poly(propylene glycol-co-fumaric acid) (PPF) for mandibular reconstruction in a rat model. The eventual intention is to use this material either as a stand-alone bone graft substitute or as an extender to autograft harvested from mandibular reconstruction sites. Materials and Methods: The PPF bone graft was crosslinked in the presence of a hydroxyapatite filler and effervescent foaming agents to develop porosity in situ by generating carbon dioxide during the effervescent reaction of citric acid and sodium bicarbonate. The latter reagents are responsible for foam formation and expansion, resulting in a polymeric scaffold with pore sizes in the range of 100 to 500 µm. Twenty adult Sprague-Dawley rats had 3-mm-diameter cortical defects decorticated on the outer aspect of their left mandibular ramus using a Hall drill. Animals were divided into 2 groups of 10 animals each. Animals in group A were treated with implantation of the PPF-based bone graft substitute. Implants were applied buccally to defects on the left side. In group B animals with similar defects, the drill holes were left to heal unaided. The amount of new bone formation and the presence of an inflammatory infiltrate were evaluated at 7 weeks postoperatively. Results: Histologic analysis of the healing process revealed enhanced in vivo new bone formation with the PPF bone graft substitute. These findings were corroborated by the histomorphometric analysis of new bone formation. Discussion: Results of this study demonstrated biocompatibility of the porous PPF-based scaffold in a mandibular defect. Conclusions: These findings may have applicability to the further development of bone graft substitutes for oral/maxillofacial applications.

Purpose: The aim of this study was to compare bone healing and crestal bone changes following immediate (Im) versus delayed (De) placement of titanium dental implants with acid-etched surfaces (Osseotite) in extraction sockets. Materials and Methods: Forty-six patients were randomly allocated to the Im or De group (n = 23 per group) and received 1 implant at the incisor, canine, or premolar region of the maxilla or the mandible. The implants were placed an average of 10 days following tooth extraction in the Im group and approximately 3 months after extraction in the De group. The widths (parallel and perpendicular to the implant) and the depth of marginal bone defects around the implants were measured clinically just after placement and 3 months later at the abutment surgery. The crestal bone changes mesially and distally to the implants were evaluated radiographically by linear measurements. Results: The survival rates were 91% in the Im group and 96% in the De group. In the Im group, the mean reductions in parallel width, perpendicular width, and depth of the largest defect of each implant amounted to 48% (from 4.4 to 2.3 mm), 59% (from 2.2 to 0.9 mm), and 48% (from 6.9 to 3.6 mm), respectively. The corresponding mean reductions in the De group amounted to 39% (from 3.1 to 1.9 mm), 77% (from 1.3 to 0.3 mm), and 34% (from 4.4 to 2.9 mm). The reduction over time was statistically significant in both groups (P .04). For both groups, a higher degree of bone healing was achieved in the infrabony defects (> 60% for depth) than in dehiscence-type defects (approximately 25%). Furthermore, 70% of the 3-wall infrabony defects with a parallel width of up to 5 mm, a depth of maximum 4 mm, and a perpendicular width of maximum 2 mm had a capacity of spontaneous healing within a period of 3 months. Discussion and Conclusion: New bone formation occurs in infrabony defects associated with immediately placed implants in extraction sockets.

Purpose: The manner in which surface roughness of implants affects bone-implant integration remains unknown. This study correlated morphologic profiles of bone-implant integration and extracellular matrix (ECM) gene expression in response to the placement of implants with different surface topographies. Materials and Methods: T-shaped hollow implants with turned and dual acid-etched (DE) surfaces were placed into rat femurs. A bone integration curve (BIC) was created from serial histomorphometric measurements within the implant chamber. The mRNA expression pattern of ECM genes in bone healing with or without implants was examined using reverse transcriptase-polymerase chain reaction. Results: At week 2, the BIC of the DE implant increased near the implant surface, whereas that of the turned implant decreased. The bone-to-implant contact rate of the DE implant was 6- and 2.5-fold higher than that of the tuned implant at weeks 2 and 4, respectively. A spatially standardized histomorphometry revealed that, at week 2, the DE implant had a greater bone volume than the turned implant in a zone near the implant, but not in zones distant from the implant surface. The DE implant evoked an accelerated mRNA expression for osteonectin and osteocalcin compared with the turned implant, along with an up-regulated expression for bone sialoprotein II, collagen III, and integrins in initial healing stages up to week 1. Discussion and Conclusion: The results indicate that different histologic bone integration profiles associated with increased surface roughness may be explained, in part, by the modulated expression of the selected ECM-related genes. The data provide evidence supporting the fact that gene regulation occurs at local levels of implant surfaces in vivo.

Purpose: Difficulties relating to bone regeneration that complicate immediate implant placement include buccal and/or lingual fenestrations, primary anchorage of the implants, and the need for protection from functional loading during the osseointegration period. The objective of this pilot study was to evaluate bone regeneration by recombinant human bone morphogenetic protein-2 (rhBMP-2) around immediate implants placed in maxillary sockets in rats. Materials and Methods: A total of 16 cylindric 0.8×1.8-mm commercially pure, solid titanium implants were placed immediately after gentle extraction of the maxillary first molar teeth of 8 male Wistar rats. The sockets were randomly divided into 3 groups: group 1 (n = 6) received rhBMP-2 with polylactic acid/polyglycolic acid copolymer-coated gelatin sponge carrier; group 2 (n = 5) received only the carrier; and group 3 (n = 5) received no grafting materials following placement. The rats were euthanized at 90 days postsurgery for microscopic analysis. Results: In group 1, the implant body remained submerged completely, including the coronal part, which was fully covered by a significant amount (30% of total height) of regenerated cortical bone, even though the implant could easily be pulled out by a tweezer at the time of placement. Close approximation between the implant surface and regenerated bone could also be detected, indicating good bone-to-implant contact. In contrast, only peri-implant bone regeneration occurred in group 2, and an approximate 0.3-mm coronal part of the implant remained exposed. When no grafting materials were used (group 3), almost one third of the total length of the implant was exfoliated out of the socket when no grafting materials were used. Discussion and Conclusions: Based on previous study and data from 16 sockets of the present study, it could be concluded that rhBMP-2 facilitated the regeneration of bone around immediate implants. In particular, the bone covering the coronal part could have been regenerated shortly after surgery, which helped to maintain the implant body inside the socket during the integration period in rats.

Purpose: In this study, the removal torques of commercially pure titanium implants that had been implanted simultaneously with the start of treatment for osteoporosis were compared to those of a group without treatment and a healthy group. Materials and Methods: Rats treated by ovariectomy or sham surgery at the age of 12 weeks were used. Twenty-eight days after surgery, the rats treated by ovariectomy were divided into an alendronate-treated group and an untreated (ovariectomy-control) group. At the start of administration of alendronate, a titanium implant was placed in the distal metaphysis of the femur. After 1 month of administration of alendronate and a vehicle, removal torque, the percentage of bone-implant contact (BIC), and parameters of treatment using alendronate were measured. Results: The removal torque values were 10.1 ± 1.6 Ncm for the group of osteoporotic rats that had been administered alendronate and 6.4 ± 1.0 Ncm for the group of osteoporotic rats that did not receive alendronate, indicating that the removal torque was significantly higher in the former group than in the latter group. However, there was no significant difference between the alendronate-treated group and the healthy control group (ie, sham surgery) (9.3 ± 1.3 Ncm). Discussion and Conclusion: These results suggested that implant placement together with treatment of osteoporosis is possible in the ovariectomized rat model.

Purpose: This study was designed to evaluate variations of bone density in designated implant sites using quantitative computed tomography (QCT) and to compare the QCT measurements to subjective evaluation of bone density. Materials and Methods: Sixty-two designated implant sites in jaws of 9 human cadavers were used. Indicator rods, 2 mm in diameter, were placed in all sites. CT images representing 1-mm buccolingual slices immediately mesial and distal to the rods were selected. Bone density (in Hounsfield units) was assessed in a standardized implant area superimposed on the images and was also subjectively evaluated by 2 independent examiners using the Lekholm and Zarb classification. Results: QCT results demonstrated that bone densities may vary markedly when different areas of a designated implant site are compared. The Lekholm and Zarb ratings for the 2 examiners showed coefficients of correlation ranging between 0.5 to 0.7 for the relationships with the QCT values. Within each of the scores used for the subjective classification, however, a wide range of QCT values was observed. Discussion: The results emphasize the importance of the use of radiographic methods prior to implant placement that allow topographically precise assessments of bone density in the region of interest. Conclusion: Access to QCT values should constitute a valuable supplement to subjective bone density evaluations prior to implant placement.

Purpose: The Zygomaticus dental implant, designed by Nobel Biocare, was developed for the treatment of the severely resorbed maxilla. Brånemark has reported an overall success rate of 97.6% with the placement of 183 implants over the last 12 years. The purpose of this article was to present a modification to the original Brånemark surgical approach to achieve better access and optimal implant placement. Materials and Methods: There are parameters within the patient's resorbed skeletal frame that guide the surgical placement of the currently used implant. However, there are shortcomings in the current surgical protocol. This report describes a simplified surgical approach in 45 patients (77 implants) using an implant with a modified head angulation of 55 degrees and a placement appliance to assist the surgeon in placing the implant as close to the crest of the edentulous ridge as possible. Results: The placement appliance identifies accurately the anatomic constraints of the resorbed skeletal frame that limit implant placement. This, together with the modified surgical protocol, has resulted in improved access and in ideal positioning of the restorative head. Discussion: The present technique allows restorative clinicians to achieve a more ideal restorative result in the posterior maxillary alveolus using the zygomatic implant, while reducing the buccal cantilever, improving tongue space, and access for maintenance. Conclusion: By placing the implant closer to the crest of the alveolar ridge using the placement appliance and an implant with a 55-degree head, the emergence of the restorative head and resultant buccal cantilever can be reduced by as much as 20%.

Purpose: Loss of alveolar bone in the anterior maxilla may preclude implant placement or compromise positioning and thus diminish the final esthetic result of the restoration. Bone augmentation can overcome such difficulties but may affect osseointegration. The aim of this study was to report the outcome of buccal onlay bone grafting in the anterior maxilla in routine dental implant practice. Materials and Methods: Seventeen consecutive patients (12 men and 5 women, mean age 31.4 years) received autogenous bone grafts from the mandibular symphysis to the anterior maxilla. A total of 35 Brånemark System MK II implants were placed in grafted bone. Results: Fifteen patients had a mean period of graft consolidation of 19.7 weeks (range 13 to 32 weeks). Two patients had simultaneous graft and implant placement; 1 implant failed to integrate in this group. This represents a survival rate of 97.1% of implants in functional loading after a mean follow-up period of 153.6 weeks from occlusal loading (range 74 to 283 weeks). Discussion and Conclusion: Mandibular block onlay grafts appear to be a predictable method for augmenting the width of the anterior maxilla prior to implant placement.

Purpose: To evaluate whether the combination of 5 surgical techniques in implant dentistry could be performed simultaneously in a predictable manner as effectively as each technique separately. Materials and Methods: Immediately postextraction, 12 wide-diameter (WD) implants were placed in maxillary first or second molar sites. The residual vertical bone height ranged between 6 and 9 mm (average 7.8 mm). An internal sinus elevation, via the osteotomy site, was carried out in 10 sites using an osteotome tool. Implants were then self-tapped into the osteotomy site followed by insertion of a customized healing screw. Consequently, horizontal gaps between the bony walls and the implant neck were filled by either bovine bone mineral or tricalcium phosphate particles. Full soft tissue closure around the healing cap screw was achieved by coronal positioning of the buccal flap. Results: Soft tissue healing around the 12 implants was immaculate. In 10 sites, internal osteotome sinus membrane elevation resulted in a height gain of between 2.5 and 6 mm (average 4.3 mm). Radiographically, bone-to-implant contact was evident. All implants were integrated and the prosthetic phase was completed after 6 months. Discussion and Conclusions: The combination of 1-stage technique and immediate placement of WD implants, along with internal sinus floor elevation and no soft tissue reflection at the time of implantation, is an achievable task and can be performed predictably. Time, cost, and morbidity are reduced, and the prosthetic solution is also eased for the benefit of the patient.

Purpose: This report evaluates the 5-year results of 9 of 10 patients in a clinical investigation of immediate functional loading of Brånemark System implants in edentulous mandibles, and of 24 patients treated with a simplified protocol for the same indication. The purpose of the paper is to suggest a simple, reliable, and documented method for immediate implant loading of complete-arch mandibular prostheses. Materials and Methods: Ten healthy patients in need of full-arch mandibular implant reconstruction (development group) were treated between December 1993 and December 1994 with 130 Brånemark System standard implants, placed in fresh extraction and healed sites. Four implants per patient were immediately loaded with acrylic resin fixed prostheses. The prostheses were replaced by metal-framework conversion prostheses approximately 6 weeks later, and definitive metal-reinforced prostheses incorporating all implants were placed after second-stage surgery. An additional 24 patients were treated with a simplified protocol using a total of 144 implants placed between March 1997 and October 2000. In these patients, the acrylic resin prostheses were not disturbed for 3 months, and fewer implants were used with an increasing ratio of implants loaded. Eventually, all implants were loaded immediately for the last patients treated. Results: The prosthesis survival rate was 100% for the total material. In the developmental group, the implant cumulative survival rate was 80% for the immediately loaded implants after 5 years, while the 2-stage implants reached 96%. Bone level measurements showed no differences between immediate and 2-stage protocols for this group. The implant cumulative survival rate was 97% for the simplified treatment group. Discussion and Conclusion: A predictable and simple concept for loading of immediate implant prostheses in edentulous mandibles was demonstrated. Results from the development of this technique suggest that it may be essential to maintain the initial implant splinting over a healing period of about 3 months and that implant placement between the mental foramina provides optimal support.

Purpose: To understand the mechanical and biomechanical behavior of dental implants, validation of stress and strain measurements is required. The objective of this study was to compare a non-linear finite element stress analysis with in vitro strain gauge measurements on strains in an implant-abutment complex. Materials and Methods: Strain gauges were bonded to an implant-abutment complex and embedded in polymethylmethacrylate resin. A force of 75 N was applied vertically and laterally in separate load cases, and strains were recorded with a strain indicator. Then, a finite element model of the strain gauge model was constructed. Contact analysis with normal contact detection and separation behavior was performed between the implant and the abutment. The same loading protocol was followed, and strains were recorded at regions where gauges were bonded. Results: Under vertical loading, the qualification and quantification of strains were similar in both methods. Under lateral loading, the measurement of strains on the abutment and in the resin were similar in both methods. However, strains on the implant collar as measured by non-linear finite element analysis were higher. Discussion and Conclusion: There is a compatibility between non-linear finite element stress analysis and in vitro strain gauge analysis on the measurement of strains under vertical loading. However, there are differences between the methods in the quantification of strains on the collar of implants under lateral loading.

Purpose: This study investigated the changes that might occur in passive tactile sensibility during a period of 3 months following implant placement in a group of edentulous subjects treated with dental implants. The effect of changing the velocity of force application on passive tactile sensibility was also investigated. Materials and Methods: Five edentulous subjects who had been treated (as a part of an immediate loading study) with 2 or more Nobel Biocare dental implants in the anterior mandible were studied. Pushing forces were applied directly and perpendicular to the long axes of the abutments until the subjects felt the first sensation of pressure, using a computer-controlled, custom-made device. The force was measured with an integral transducer. The applied force had a ramped staircase pattern, which was used at 2 different tip velocities. The measurements were taken on 4 occasions: 1, 2, 4, and 12 weeks after fitting the abutments. Results: Statistical analysis, using multilevel modeling, demonstrated that there was a significant decrease in the tactile threshold over successive weeks following implant placement. It also demonstrated that high velocity exhibited a higher threshold than low velocity. Discussion and Conclusion: It could be concluded that there was a significant increase in passive tactile sensibility during the healing phase following implant placement.

Purpose: The purpose of this study was to record the effectiveness of Gold-Tite square abutment screws, tightened to 35 Ncm with a torque indicator, in maintaining a clinically stable implant/abutment connection. Materials and Methods: The study consisted of 73 patients who were treated with 110 Osseotite implants. All patients were restored with either pre-machined titanium or customized UCLA hexed abutments. All abutments were fabricated per the Gold Standard ZR abutment design of Implant Innovations. All of the abutment screws were Gold-Tite square abutment screws. They were torqued to 35 Ncm with a torque indicator at the time of abutment connection. All crown restorations were cemented to the abutments. Patients were followed for at least 1 year post-occlusal loading. Results: Four patients with 6 implants were lost between the 6- and 12-month recall appointments. Clinical assessments of implant/restoration mobility were made by the author. One abutment screw was found to be loose at the 12-month recall appointment, representing a 99% survival rate. Discussion: These results add to the growing evidence that abutment screws with enhanced surfaces may provide increased screw/implant contact, higher rotational values, and calculated preload values. Conclusion: The use of the Gold-Tite square abutment screws, torqued to 35 Ncm, maintained a stable implant/abutment connection that was successful in clinical practice for this minimal evaluation period.

Purpose: The aim of the present study was to evaluate the potential application of 2 types of microfocus x-ray units to study the bone structure around dental implants and at the bone-implant interface. Materials and Methods: IMZ titanium implants were placed in the maxilla and mandible of a beagle dog. After implantation periods of 1, 2, and 3 months, the bone-implant interface was evaluated with microfocus x-ray computed tomography (CT) and microfocus x-ray fluoroscopy. Results: Microfocus xray CT images of the bone-implant specimen at 3 months after implant placement revealed a clear distinction between the implant and the bone. The implant surface was partially covered with bone, and direct contact between the implant and bone could be clearly seen. Differences in degrees of calcification were identified by the differences in relative black and white intensity. Microfocus x-ray fluoroscopy also showed clear features of the bone and titanium implant. The original drill hole and new bone formation could be recognized. These findings corresponded with traditional histologic observations by light microscopy. Discussion and Conclusion: Microfocus x-ray techniques are non-destructive and require a very short examination time. They are considered useful to observe details of the bone structure and bone-implant interface. Microfocus x-ray fluoroscope and microfocus x-ray CT techniques can provide a clear and distinguishable image of the bone-implant interface because of their high spatial resolution.

Purpose: The aims of the present study were to use polysomnographic analysis to confirm sleep bruxism (SB) and to evaluate clinical findings of dental implant treatment in SB patients. Materials and Methods: The present study comprised the retrospective analysis of 368 patients with a total of 838 endosseous implants. Nineteen patients who experienced mechanical complications, such as implant or abutment fractures, loosened gold screws, or occlusal surface wear or damage, were selected for polysomnographic analysis to monitor sleep symptoms. Six patients in the study group were identified as having SB, and this was confirmed by polysomnographic analysis. Results: The SB electromyographic episodes were at least 20% of the patients' maximum voluntary contractions while awake and were scored. Most of the bruxism episodes (80%) were seen in light sleep stages. Only 5% of bruxism episodes were detected during rapid-eye-movement sleep. Sleep stage recordings were similar in all individuals. Bruxism episodes did not cause arousals. Patients were unaware of their nocturnal parafunctional habits. Despite protection with night guards, all patients were reported to have continued bruxism. Discussion: Since possible occlusal parafunctional habits may be evident in any stage of dental treatment, treatment outcome risks must be considered. Conclusions: Polysomnographic study was evaluated as an effective, low-cost method to confirm occlusal parafunctional habits during sleep. Precautions against SB in patients having dental implant treatment have not been properly clarified. However, night guard protection appears to have some validity in patients having sleep bruxism.

Vertical augmentation of the alveolar ridge is intended to restore resorbed alveolar ridges. This procedure is important for the placement of dental implants in a favorable position and also to enhance restoration esthetics. This article presents an approach for vertical ridge augmentation in the anterior maxilla utilizing symphyseal bone cores. A patient presented with 2 localized bony defects around the maxillary lateral incisors. Following extraction of these teeth, vertical bone defects of 7 mm on the right and 6 mm on the left were observed in relation to the cementoenamel junction of the adjacent teeth. Two bone cores were harvested from the mandibular symphysis using a trephine. These bone cores were tapped into 2 predrilled osteotomy sites with corresponding diameters until stabilization was achieved. The 2 sites were grafted with demineralized freeze-dried bone allograft and a titaniumreinforced expanded polytetrafluoroethylene membrane. After 5 months, the membranes were removed and vertical ridge augmentation of 5 mm on the right and 4 mm on the left was observed. The width of the ridge was increased as well. Two implants were placed in favorable positions, restored after 6 months, and followed successfully for 1 year after loading. This technique represents a viable approach for augmentation of deficient alveolar ridges prior to the placement of dental implants.